Antibiotics III

Question 1

Ciprofloxacin (2nd gen.), Levofloxacin, Gatifloxacin and Moxifloxacin all inhibit DNA synthesis and are members of the class of antibiotics known as _____.

Answer 1

Fluoroquinolones

Question 2

What do fluoroquinolones target in G- and G+ organisms, respectively?

Answer 2

G- = Gyrase

G+ = Topoisomerase IV

Question 3

What added constituent of the fluoroquinolones increases their antimicrobial activity

Answer 3

Fluorine

Question 4

Which fluoroquinolone is most effective against G- organisms?

Answer 4

Ciprofloxacin

others equal in efficiency, but less than cipro

Question 5

T/F Cipro is the most effective quinolone against G+

Answer 5

FALSE

Cipro is the least effective quinolone against G+ organisms. Others are equal in efficiency, and more effective than cipro.

Question 6

From least to most, order the quinolones in regard to their actiity against anaerobes.

Answer 6

Cipro

Question 7

What kinds of infections are quinolones used to treat (6)?

Answer 7

1) UTI
2) Prostitis
3) GI/Abdominal (Traveler’s diarrhea, Shigellosis, Typhoid)
4) Respiratory (Atypical pneumonias [mycoplasma], S. pneumoniae)
5) Bone/joint/soft tissue (Chronic osteomyelitis, polymicrobial diabetic ulcers)
6) STDs (chlamydia, chancroid)

Question 8

Which STDs are never treated with fluoroquinolones due to resistance?

Answer 8

Syphilis and gonorrhea

Question 9

Which organisms are beginning to gain resistance to fluoroquinolones (3)?

Answer 9

1) S. aureus
2) P. aeruginosa
3) S. marcescens

Question 10

Which fluoroquinolone is used to treat anthrax and tularemia?

Answer 10

Ciprofloxacin

Question 11

Combinations of fluoroquinolones are used to treat _____ or for _____

Answer 11

Atypical mycobacteria or neutropenic prophylaxis

Question 12

T/F Fluoroquinolone is administered via IV

Answer 12

FALSE

Administered orally (can send patients home with it!)

Question 13

Metronidazole and Nitrofurantoin is under the class of antibiotics known as _____

Answer 13

Nitroimidazoles

Question 14

What is metronidazole’s mechanism of action?

Answer 14

Converted to radical iron by ferredoxin, causing fragmentation of DNA

Question 15

Metronidazole is used to treat _____ and _____.

Answer 15

Strict anaerobes (c. diff)

Parasites (trichomonas, giardia, entamoeba)

Question 16

T/F Metronidazole can’t be used against organisms that use oxygen, including facultative anaerobes

Answer 16

TRUE

These organisms have the biological components to deal with free radicals

Question 17

Nitrofurantoin is used almost exclusively to treat _____ or _____

Answer 17

Cystitis or lower UTIs

Question 18

Nitrofurantoin is effective against many _____ bacteria except _____, AND _____

Answer 18

Effective against many GRAM - bacteria except PROTEUS AND PSEUDOMONAS

Question 19

The sulfonamides function as _____ antagonists

Answer 19

Folate antagonists

Question 20

Sulfonamides are competitive inhibitors of _____

Answer 20

Dihydropterate synthase

Question 21

The enzyme sulfonamides competitively inhibits (dihydropterate synthase) is needed for the production of _____. Blocking this enzyme prevents the organism from _____.

Answer 21

Dihydropterate synthase is needed for the production of THF

Blocking this enzyme prevents the conversion of uracil to thymidine by the organism

Question 22

What are the mechanisms of bacterial resistance to sulfonamides?

Answer 22

1) New folic acid pathway
2) Altered affinity of enzyme for drug
3) Efflux

Question 23

Sulfonamides are concentrated in _____, making them _____ in this location

Answer 23

Concentrated in urine (great for UTIs!)

Bactericidal there

Question 24

Which sulfonamide is used for opthalmologic infections?

Answer 24

Sulfacetamide

Question 25

Which sulfonamide is used to prevent infection and treat infection of burn wounds?

Answer 25

Silver Sulfadiazine

Question 26

What are the therapeutic uses of Sulfonamides (4)?

Answer 26

1) UTI 2) Nocardiosis 3) PJP (sulfamethoxazole + trimethoprim [bactrim]) 4) Toxoplasmosis

Question 27

Rifamycins are _____ spectrum

Answer 27

Broad spectrum

Question 28

Which rifamycin is used for HIV+ patients?

Answer 28

Rifabutin

Question 29

What are the therapeutic uses of rifampin (3)?

Answer 29

1) TB 2) Staph 3) Meningococcus prophylaxis

Question 30

What are the therapeutic uses of ridabutin/rifapentine (2)?

Answer 30

1) TB in HIV+ | 2) MAC

Question 31

T/F Rifaximin is readily absorbed in the gut.

Answer 31

FALSE Rifamixin is limited to the lumen of the gut

Question 32

What is the mechanism of action of rifamycins?

Answer 32

Inhibit DNA-dependent RNA polymerase

Question 33

How is bacterial resistance to rifamycins achieved?

Answer 33

Alteration of target (DNA-dependent RNA polymerase)

Question 34

What is the mechanism of action of daptomycin?

Answer 34

Depolarizes bacterial membrane > K+ efflux > death

Question 35

What kind of organisms does daptomycin cover?

Answer 35

Aerobic G+ cocci (except Pneumonias - drug inactivated by lung surfactant) - Works against MRSA, MSSA, VRE

Question 36

What is the mechanism of action of Polymyxins?

Answer 36

Membrane detergent

Question 37

What kind of organisms do the polymyxins cover? What are the exceptions?

Answer 37

G- organisms EXCEPT Proteus, Serratia, Burkholderia

Question 38

Which polymyxin is nephrotoxic?

Answer 38

Polymyxin E

Question 39

What are the first line anti-mycobacterium antibiotics?

Answer 39

Rifampin Isoniazid Pyrazinamide Ethambutol RIPE Therapy (Streptomycin)

Question 40

What are the second line anti-mycobacterium abx?

Answer 40

``` Cycloserine Amikacin Moxi/Gatifloxacin Ethionamide Aminosalicylic Aid Linezolid ``` CAME to Alleviate Lung

Question 41

Isonazid (INH) prevents the synthesis of _____

Answer 41

Mycolic acids

Question 42

Is isoniazid bactericidal or bacteriostatic?

Answer 42

Trick question. It's both. Bactericidal for growing cells Bacteriostatic for resting cells

Question 43

Isoniazid (INH) is a prodrug that requires _____ for activation

Answer 43

Catalase peroxidase

Question 44

Ethambutl inhibits _____ involved in cell wall synthesis of mycobacterium

Answer 44

Arabinosyl transferase

Question 45

Pyrazinamide is bactericidal at _____ pH, as in a macrophage or phagolysozome

Answer 45

Acid pH

Question 46

What gene is inactivated by pyrazinamide?

Answer 46

Fatty acid synthase I gene

Question 47

Which antimycobacterium drug targets the C subunit of mycobacterium ATP synthase?

Answer 47

Bedaquiline (Resistance is acquired by mutating the C subunit)